'Glowworms in sky' studied at Starfire Optical Range

KIRTLAND AIR FORCE BASE, N. M. (AFPN) -- An Air Force Research Laboratory
astronomer calls them "glowworms in the sky" and scientists will soon
gather at the laboratory's Starfire Optical Range to study them.

Between Nov. 16 and 19, scientists will gather at Starfire to train a
variety of instruments on the Leonid meteor shower. Grains of sand and
dust from the comet Temple Tuttle produce these meteors. Named for the
constellation Leo, from which they appear to emanate, these meteors
vaporize in the Earth's atmosphere.

According to Dr. Jack Drummond, the laboratory's Directed Energy
Directorate astronomer, the Leonid meteors leave behind trails which,
unlike ordinary meteors that fade in a matter of seconds, can last up to
an hour and are still unexplained.

"I call these lingering meteor trails 'glowworms in the sky' since they
are not only visible for minutes by chemical reactions, but are twisted by
the winds into serpentine shapes, appearing like snakes or worms,"
Drummond explained.

Scientists hope to gather enough information to explain one of the more
curious atmospheric phenomena -- What makes the meteor trails glow?

The glow, called chemiluminescence, is the production of light from
chemical reactions similar to bioluminsescence, the same kind of glowing
reaction found in biological entities such as fireflies and their larvae,
glowworms.

Drummond, who last year guided lasers onto the trails when they appeared
last November, said the lingering meteor trails are self-luminescent.

"They do not shine by reflected moonlight or sunlight," he said, adding,
"but the exact chemical reactions involved are unknown."

The scientists will direct a lidar, a laser that operates at visible
wavelengths to gather data, onto the lingering trails. This instrument, on
loan from the University of Illinois, was steered onto meteor trails last
year to probe the meteors' compositions.

The data gathered by the lidar, which is attached to the 3.5-meter
telescope at Starfire, indicates that although sodium may be involved in a
catalytic reaction with ozone to produce sodium airglow, it is not the
principle emission from the trails.

This year, additional instruments will be used to try and identify the
emission lines. Three spectrographs will be aimed at the trails to try and
determine the chemical reactions that are responsible for the glow.

A spectrograph divides light into a color spectrum, revealing bright
(emission) and dark (absorption) lines produced by elements and molecules.
The operation of two spectrographs, one from the University of Arizona and
one from the University of Illinois, will study light visible to the naked
eye. The third spectrograph, from Aerospace Corporation, will study light
in the infrared at wavelengths that are not visible to the naked eye.

An electronic charge-coupled device camera and video camera will be used
to record the changing appearance of the trails. Shown at several
conferences, last year's 13-minute video, "blew the audiences away,"
according to Drummond. He said most people have never seen or heard of
these 'glowworms in the sky' which are characteristic of the Leonid Meteor
showers.

The scientists hope to answer why the 'glowworms' are peculiar to the
Leonid storm periods, which occur every 33 years, and why they are rarely
seen at other times. They wonder if it may imply something about the
composition of the parent comet.

Although this year's shower is expected to peak over Europe on the morning
of Nov. 18, it is hoped that some of the fireball components of the storm
will be visible locally one or two days before or after the main peak.
Here, on a dark quiet mountaintop on the southern end of Kirtland Air
Force Base, N.M., scientists will be watching, waiting and hoping to
unravel a mystery occurring 60 miles overhead.